dipole
ANTENNA EXPERIMENT
ON Saturday 12-1`and Sunday 13-1 I have made a temporary experimental dipole antenna with active elements of 12 m and 16 m. Wire used is 0.5m single copper wire
Receiver connection [say here twin wire ] cable was a twin , stranded copper wire , of 0.15 mm each wire, length is about 6 m.
Dipole has been constructed having the same lengths for both parts however due to constraints of the garden a small part of the antenna has been folded
As the system is only temporary , I have supported this antenna into natural supports. Left part ( the 16 m is suppored by another wire of same type , about 3 m and this over two antenna TV cables in order to be a little high.( abt 3 m from the ground) This connected to the balckpart of the twin wire
The other part is supported by 3 tress on nearly the same height but about 3.5 m of length has been wound due to constraints of the garden.This connected to the red part of the twin wire
This isáá the firstá experiment . Later this year i intend to install a á multiband inverted V ( 5 dipoles connected tp a main) over the roofá for a maximum length ofá 20 m perá pole ( fixed installation)
Two series of tests have been made :
Comparative dipole cs 16 m wire testing
Same testing but MFJ antenna tuner 16010 has been used
Results as opinion form:
Mysteriously when reversing theá æpoles' on the radio R75 æ is like using two diferent antennas , even when using the antenna tuner. Different signal levels and different noise levels and sometimes directivityá It seems that ground does not play its role correctly (?)
Possbly due to very thin wire , most signal levels are lower than single wire antenna. I am correct? If thiis is true this diference can be 6 db lower dur to surface only.
At several bands though signal levels are lower than single wire antenna in most cases have lower noise levels . As in example 7120 IRRS at 0915 shown levels below S1 unit - still with the antenna tuner - but was noise free . IN contrast to it the single wire antenna shown levels of S3 full of noise ( no signal was audible) IN another example R cochiguaz 2120 on Sat 13 was audble ( still as marginal) only with the dipole
Dipole has enhanced reception in my most un-useful bands: LRA Argentina feeeder at 29810 has 3 S units higher level than single wire More particularly: 29-25 , 14-13, 11-10 , 4-3, 1.6 Mhz shown enhanced receptioná
IN the highest bands both a capacitance and inductance are required to tune the dipole . IN the lower bands ( from abt 7 Mhz and lower) only inductance is required . On 9 MHz different antenna tunings are required between the single wire and dipole
Here are the measurements:
Legend:
AB black red ( connected to input / ground correspondingly)
BA red black
Red: pole from the tree side
Black: the free to air wire
IN all these cases cables are connected to the 300 Ohm input
Measurements without antenna tuner
180 5 5 5 245 3.5 3 4.5 1448 7 3 5.5 1456 7.5 6 7 3870 9 7 3890 7.5 7 5 3945 7.5 7 3.5 4060 9 clr 7 5 QRN 5050 3.5 5.5 9 6060 0 0 7 6085 3 1.5 9 6460 4 9 7105 9 5 7 7120 0 0 4 only QRN 7160 3 2 6 much QRN 7250 +10 7265 4 3 5 7560 3.5 3 7 9320 4 4 7 11585 8 8 8 12015 6 5 2 14020 9 9 7 15172 9 AB 9 noise BA 9+10 16m 15630 5 QRN 7.75 clr 7 15685 2 AB 2BA 5 17548 7 5 5 21455 6 6.5 21660 7 5-7 3
measurements with antenna tuner MFJ 16010
268 4 3 4 747 8 9! 7 1600 9.5 9 8 5161 tty 8 4 5 5796 6 4 7 6060 2 5 full QRN 6165 5 6 7120 3@+10 3 7265 5 7 9515 7 7.5 11300 4 5 - 15000 5 4 6 15310 5 4 6 17335 7 5 6 21465 8.5 5.5 21845 8 5 25740 9 5 25740 9 10
